The friends and family of Anne Smedinghoff are mourning the 25-year-old Foreign Service Officer killed in a car bomb blast in southern Afghanistan whom they describe as vivacious and loving.

Smedinghoff was one of five Americans killed in a suicide bomb attack in Qalat, Zabul.

Working as a press officer for the U.S. embassy in Kabul, she was helping Afghan journalists cover an event at a boys school where the local U.S. Provincial Reconstruction Team was to donate math and science books

The other Americans killed in the attack were three military service members and a civilian working for the Defense Department. Four State Department officials, including one described as critically injured, were among the 10 injured in the attack.

"The world lost a truly beautiful soul," Tom and Mary Beth Smedinghoff said in a statement. "Anne absolutely loved the work she was doing" as a press officer at the U.S. embassy in Kabul, they said.

Having served in the Foreign Service for only three years, Smedinghoff volunteered to serve in Afghanistan and arrived last July.

"We are consoled knowing that she was doing what she loved, and that she was serving her country by helping to make a positive difference in the world," her parents said. "She was such a wonderful woman -- strong, intelligent, independent, and loving. Annie, you left us too soon; we love you and we're going to miss you so much."

A senior State Department official who also knew Smedinghoff described her as being "really special," "sweet," and "very bright."

Traveling in Istanbul, Secretary of State John Kerry described Smedinghoff's death as the "stealing of a young life."

"There are no words for anybody to describe the extraordinary harsh contradiction of a young 25-year-old woman with all of the future ahead of her, believing in the possibilities of diplomacy, of changing people's lives, of making a difference, having an impact, who was taking knowledge in books to deliver them to a school. And someone somehow persuaded that taking her -- his life was a wiser course and somehow constructive, drives into their vehicle and we lose five lives," Kerry said.

Kerry had met Smedinghoff two weeks ago during his recent trip to Afghanistan, where she had been assigned to coordinate his trip.

"I remember her as vivacious, smart, capable, often chosen by the ambassador for her capabilities," Kerry said. He said of his call to Smedinghoff's parents on Saturday that "there is no harder conversation to have in the world."

Afghan security officials told ABC News that the State Department convoy had just left its headquarters in Qalat and joined the convoy of the local provincial governor who was also headed to the school book giveaway.

That's when two suicide attackers attacked the convoy. The security officials said there was an initial car bomb detonated by a remote device. Then a suicide bomber wearing a suicide vest appeared and caused more casualties.

Afghan sources say the school event had been announced a day in advance, which possibly allowed attackers enough time to plan the attack.